Revolutionizing wood permeability via microwave-initiated persulfate activation

Abstract

Poor penetration of modifying reagents in wood due to the influence of extractives and pits in the wood. In this paper, microwave-activated sodium persulfate (MW-PS) solutions were used to remove extractives from fir heartwood and to disrupt pit membranes to improve the permeability of the liquid in wood. The large amount of energy generated by microwave irradiation decomposed S2O82- into SO4·-, while some of the resulting SO4·- combined with H2O to form·OH. The permeability of the liquid in the wood cells and cell wall interstices was increased by oxidative decomposition of the wood extractives by free radicals. The moisture in the wood absorbs the large amount of energy released by the microwaves, vaporizes and expands, destroying the pit membrane and creating new liquid channels. Microwave-activated persulfate-treated fir heartwood not only had a significantly lower extractive content (47.45%), but also an increased average pore size (91.84%). The most important thing is that the penetration of liquid into the fir heartwood was significantly increased (63.45%).